Despite the extreme accuracy of machining operations and their high level of reproducibility, adjustments almost always have to be carried out, either during assembly operations, or, more frequently, during fine-tuning or finalising operations, in particular to set the unbalance and adjust inertia in the case of moving parts, and to set the frequency in the case of an oscillator.
It is particularly at the assembly stage that it is necessary to fine tune the pairing of certain components which, taken independently, are within machining or manufacturing tolerances, but which cannot be assembled purely and simply because of operating constraints peculiar to the sub-assembly or completed assembly.
This is particularly true of timepiece regulating members and more particularly of sprung balance assemblies. It seems, in fact that adjustments of unbalance and inertia settings, both static and dynamic, are already very difficult at the individual component stage, and that these fine tuning operations become extremely complex when the components are assembled to each other. In particular, dynamic adjustments are difficult to implement.
Various techniques are known for adjusting a sprung balance sub-assembly, two of which are most commonly used.
The “omega metric” system consists in:                grading the balance springs;        grading the balances;        pairing a balance chosen from a particular grade with a balance spring also selected from a particular grade, where said grades are compatible with each other.        
This method requires a large stock of components and grades which are relatively broad.
Alternatively, the “Spiromatic system” is known:                generally a balance spring is assembled on a balance;        the balance spring is cut to the right length, to obtain a torque suited to the inertia of the balance.        
It is not possible with this method to guarantee the precise end position of the spring, resulting in a loss of chronometric performance.
These conventional techniques are either expensive, or mediocre as regards the accuracy of the results obtained.